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I don't totally understand what registering a class for cell reuse does. I understand how we use reuse identifiers on cells, I just don't understand what calling this method in viewDidLoad does. Looked at a bunch of docs. Not clicking, n00b here. Could someone give me some tips on what it does please?
TableViewController.m
- (void)viewDidLoad {
[super viewDidLoad];
// Register Class for Cell Reuse Identifier
[self.tableView registerClass:[UITableViewCell class] forCellReuseIdentifier:CellIdentifier];
}
882
dequeueReusableCellWithIdentifier . Instead of creating every single cell and then selectively displaying them, we only create a handful of cells, enough to fill the screen and a little more. As we scroll, we reuse the cells offscreen, leading to a much more memory efficient task.
The reuse identifier is associated with a UITableViewCell object that the table-view's delegate creates with the intent to reuse it as the basis (for performance reasons) for multiple rows of a table view. It is assigned to the cell object in init(frame:reuseIdentifier:) and cannot be changed thereafter.
There are two variants to register , but both take a parameter called forCellReuseIdentifier , which is a string that lets you register different kinds of table view cells. For example, you might have a reuse identifier "DefaultCell", another one called "Heading cell", another one "CellWithTextField", and so on.
This method dequeues an existing cell if one is available or creates a new one using the class or nib file you previously registered. If no cell is available for reuse and you didn't register a class or nib file, this method returns nil .
In the cellular reuse concept, frequencies allocated to the service are reused in a regular pattern of areas, called "cells", each covered by one base station. In mobile-telephone nets these cells are usually hexagonal. To ensure that the mutual interference between users remains below a harmful level, adjacent cells use different frequencies.
Principles of cellular frequency reuse In the cellularconcept, frequencies allocated to the service are re-used in a regular pattern of areas, called 'cells', each covered by one base station. In mobile-telephone nets these cells are usually hexagonal. In radio broadcasting, a similar concept has been developed based on rhombic cells.
Frequency Reuse. Frequency Reuse is the scheme in which allocation and reuse of channels throughout a coverage region is done. Each cellular base station is allocated a group of radio channels or Frequency sub-bands to be used within a small geographic area known as a cell. The shape of the cell is Hexagonal.
Cellular Frequency Reuse JPL's Wireless Communication Reference Website Chapter: Cellular Telephone Networks Cellular Radio Cellular phone networks use cellular frequency reuse. In the cellular reuse concept, frequencies allocated to the service are reused in a regular pattern of areas, called "cells", each covered by one base station.
You have a UITableView. It has a datasource that provides it UITableViewCells. To save memory and processor cycles, it unloads UITableViewCells that are no longer on screen and puts them into a reuse queue. When it loads a new cell, the datasource will typically ask the UITableView for a cell from this reuse queue. If the queue is currently empty, UITableView will construct a new UITableViewCell using the class provided. The reuseIdentifier is used to distinguish this particular cell type queue from another cell type queue within the same UITableView.
Something like this:
UITableView: "Hey, Datasource! Give me the cell for this indexPath."
Datasource: "Alright. That's a 'foo' kind of cell. Got any of those kicking around that you're not using?"
No class registered; reuse cells returned from datasource previously
UITableView: "Yes, I do. Here you go."
No class registered; no cells available
UITableView: "Nope. Hey, I don't have a class registered for that kind of cell. Hmm. Here's nil instead."
Class registered; reuse cells returned from datasource previously
UITableView: "Yes, I do. Here you go."
Class registered; no cells available
UITableView: "Nope. But I have a class registered for that identifier. Here's a new instance."
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